This invention relates generally to seat adjusters, and more specifically it relates to an articulated mounting for reclinable backrests of a seat, especially a motor vehicle seat having a stationary hinge part assigned to the seat and a rotatable hinge part assigned to the backrest and connected to the stationary hinge part by means of a pivot axle. The angular position of the two hinge parts is defined by means of an adjustable arresting device in the form of wobble gears which include an eccentric member which is carried on a non-circular coupling section of the pivot axle. The eccentric member supports one of the wobble gears and its eccentricity defines the point of engagement of the teeth of the wobble gears.
In prior art articulated mountings of the aforedescribed type, the adjustment shaft has a section provided with a wedge-like surface which is surrounded by an eccentric member having also an inclined surface cooperating with the wedge surface of the adjustment section of the shaft. The eccentric member supports for rotation a spur gear provided in one hinge part of the articulated mounting, the spur gear being in mesh with a geared rim provided in the other hinge part of the mounting and forming therewith the aforementioned wobble gears. The pivot axle is axially displaceable and its adjusting section is spring-loaded in a direction in which it increases the eccentricity of the eccentric bushing. The biasing spring means acting in the direction of eccentricity urge the wobble gears into their engagmement point without any blacklash so that rattle-proof arresting of the mounting parts in their adjusted position is insured. The control handle or wheel which is rotatably connected to the pivot axle has in its hub portion a diametrally extending groove, the bottom surface of which is provided with a correspondingly diametrally directed recess. This recess in the position of the pivot axle in which the eccentric member is locked accommodates projections of the pivot axle which by lifting the handle and turning it about a minute angle abut against the bottom surface of the recess in the handle. In doing so, the adjustment section is slightly shifted in axial direction against the force of the spring means opposite the eccentric member to relieve the latter so that any play between the wedge surfaces of the adjusting section and the collar-shaped eccentric member on the one hand, and between the teeth of the wobble gears on the other hand, can be adjusted so that the adjustment of the angular position of the articulated mounting members can be effected with minimum force. Nonetheless, the advantage of an easy operation of the control lever during the adjusting and arresting process of the wobble gears resulting from the elimination of any play of the wobble gears in the rest condition of the articulated or hinge mounting, is outweighed by the necessity of employing a relatively large number of additional structure elements requiring a relatively large construction space and especially resulting in a considerably increased depth of the hinge mounting structure. In addition, the manufacture of these parts and their assembly into the completed hinge mount is expensive so that this expenditure, which achieves merely a limited operational ease during the adjustment process of the articulated mountings, seems in many cases unjustified.